Train stop and cab signal system



July 11, 1933.

A, E. HUDD TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1, 19283 Sheets-Sheet 1 TO BEA/ 5 nn/c4702 MILL e 23 To EPA/(E PIPE July 11,1933. A. E. HUDD TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1,1928 3 Sheets-Sheet 2 L J1 1L H H H H 5i l'lllllllllllillllllllllllllNEUNII.

1 lllllllllllllllll-lllll'11lll Inuit-1h H1 red E Hudd {i July 11, 1933.A. E. HUDD 1,917,372

TRAIN STOP AND CAB SIGNAL SYSTEM Original Filed Aug. 1, 1928 3Sheets$heet 3 Inuen cu- FUJI-ed E. Hudd Patented July 11, 1933 UNITEDstares PATIENT, OFFICE ALFRED nnnns'r HUIDD, 01" sunnlron, ENGLAND,Assrsnon, BY MESNE ASSIGNMENTS,

TO ASSOCIATED ELECTRIC LABORATORIES, ING, OF CHICAGO, ILLINOIS A CORPO-sermon on DELAWARE TRAIN STD]? AND GAB SIGNAL: SYSTEM Griginalapplication filed August 1, 1928,.Seria1 No. 296,652. Divided and thisapplication filed November 16, 1931.

The present invention relates in general to train stop systems, but isparticularly concerned with the provision of a train stop system of theintermittent inductive type and wherein cab signals are provided forindicating the t'rallic conditions ahead, and is a division or" theco-pending Huddapplication, Seriai'ilo. 296,652, filed August 1, 1928.

Some ott'the main features of the present invention are to provide asystem of circuits and mechanism on a locomotive for giving threedistinct signalling indications in the cab, for indicating as manydifferent trallic conditions ahead and for giving these indicationsindependently of, or in conjunction with, a train stop system; toprovide a system of the foregoing character which requires but onereceiver relay or impulse receiving unit on the locomotive and only twotrackway elements for each block ofthe trackway'; to provide a 'trackway.elec-tromagnet capable of producing, alternatlvely, either of twomagnetic fields at right angles to each other ;'and

v in fact, to provide an extremely simple train The valve structurediagrammatically dis-' closed in the upper part ofFig. 1 is a some whatsimplified modification of that shown in the co=pendinglielly'application, Serial No. 292,996, filed July 16, 1928. This valve,like the one in the former application, is designed for insertion inthebrake line in substitution for the double heading cock, a double headingcock being part of the present'valv'e strum ture. The purpose ofthisvalve is to initiate an automatic service application of the Serialin. 575,250.

brakes to prevent the release of an auto: natlc-brake application untila predetermined time'interval has elapsed, and to permit an emergencyapplication otthe brakes at any tlme.

This valve has a .mainbody' 6, having'an opening 7 for connection w1ththe usually provided brake'applicator and an opening 8' for connectionwith the brake pipe line. Inside the valve body, a number of ports10-14, inclusive,,are provided-all of which extend from a milledsurface, forming a slide valve seat, 15. The port 10 connects with theopening 8 and has a branch 10 connecting with a secondportion of thevalve body which will-subsequently be described. The portll extendsdownward a short distance from the seat 15 and then connects withatmosphere. "The port 12 extends directly downward and connects withatmosphere.

he port 13'extends downward parallel to the port 12, but is connectedwith a timing res ervoir 50, The port 14- extends downward a shortdistance and then extends horizon-- tally into connection with-a port19; The right portion of the valve body has a slide valve seat 36provided with a large exhaustport 37 and in which seat the other end ofthe previously mentioned port 10 terminates.

The left portion of the valve structure. is

in the form of a cylinder, in'which is mounted an automatic brakeapplying piston 19', hav ing connected. to the right thereof, a slidevalve' member20, which lies against the valve seat 15 of the valve body.Connected with the leftpart of the piston 19 is a cup-like membercontaining a compression spring 21. The cup-like member on the piston 19telescopes into a second cup-like member 70 forming an air chamber 71within these cup-like membersand a secondary air chamber 72 surroundingthese cup-like members Two orifices, 22 and 23, connect these. chambers,

while an orifice 24 connects the'chamber 71 with the opening 7;Immediatelybelow and forming a part of chamber 72 is an extended portionof the valve body having a port 49 connecting with an exhaust whistle 5.The port a9 is adapted to be normally maintained closed by an associatedelectropneumatic.

valve EPV when energized. A cut-out element 28 is, however, providedwhich may be turned up to mechanically close the port 19. This cut-outin practice is ordinarily provided with a seal, which nrust be brokenbefore the same can be turned up to cut out the control by theelectropneumatic valve EBV. :Referringncw to the right portion of thevalve member, a dividing member 9 serves as a bearing for a shaft 31,carrying the valve member 20 and as a stop for an emergency pistonreturn spring 33. Immediately to the right of the spring 33 is anemergency brake applicator piston 32'. the slide valve member 34 over aslide valve seat 36, and at right angles jito port 101 is a doubleheading cock having ahandle 43.

7 With the electropneumatic valve energized, which is its normalcondition, the air supply for holding the brakes released passes.

through the usual brake applicator valve (not shown) into opening 7 ofthe brake valve structure, through the passage 7' of the slide valvemember,through port and the openmg of .thedouble heading cock andthenceinto the opening 8 and into the brake pipe line; Owing to theorifices 22 and 23, brake pipe pressure is also built up in chambers7land 72. Also because of the orifices in element 9 and piston 32, brakepipe pressure is built up on both sides of the piston 32. The springs 21and 33 are therefore normally effective to hold the pistons, 19 and 32to the right in the position in which they are shown. If theelectropneumatic valve EPV is de'energized, air exhausts through theoutlet port 49 and through the. whistle 5 at a greater rate than brakepipe air is permitted to enter chamber 72 through the restrictedorifices 24, 23, and 22. Consequently, after the pressure inchamber '52falls to a point where the pressure upon the right-hand side of theservice application piston 19issufiicient to overcome thespring 21 inchamber 72 (approximately six seconds, as designed) the service brakeapplication piston 19will begin to move and will first close orifice 23.I When the orifice 23.closes, the air supply to chamber 7 2 isgreatlyreduced and the piston 19 with the slide valve member willquickly move to the extreme left. a e

' The piston carries with it the slide valve 20,

which, in its operated position, closes the air path formerly existingbetween openings 7 and 8 and connects the latter opening to at inosphereby way of the port 10, passage 90, and exhaust port 11, to produce anautomatic brake application. The slide valve member also disconnects thetiming reservoir from c dnnection with atmosphere by way of ports 13 and12 and instead connectsthis reservoir with port 14 for a purpose whichwill subsequ ently be made clear.

i To restore the piston 19 and slide valve This piston operates member20 to their initial position, the elec tropneumatic valve EPV must beagain energized to close the port 49. This permits the pressure on theleft of the'piston 19 to again build up to approximately that'on' theright of this piston. The capacity of chambers 71 and 72 is very limitedand in order to prevent practically immediate automatic release of thebrakes following the energiz ation of the valve EPV the timing reservoirwas brought into communication with the chambers 72 and 71." Because ofthe restricted orifice 22 and the capacity of reservoir 50 anappreciable time elapses after reenergization of the electropneumaticvalve before the piston 19 and its valve member are returned. Thereceiver relay shown in the lower half of Fi 1 is of the same generalcharacter as that shown in the co-pending Hudd applica tion, Serial No.281,656, filed May 31, 1,928.

The present'relay, however, has somewhat differentmagnetic circuits andhas three arma tures instead of two. Therelay is built into anon-magnetic casing 51, which is suspended from a vehicle in inductiverelation with the track magnets shown in Figs. 2 to 5A,inelusive, andwhich will be described later. The relay consists of three inductorplanes 52, 53, and 54, having pole pieces 7783, for attracting threearmatures 55, 56, and 57. The

free endsof armatures are of north polarity, being polarized so by asmall permanent magnet 58; the free ends of-armature 56 are of southpolarity, being so polarized by the action of the permanent magnet 58and asecond permanent magnet 59, while the free ends of armature 57 areof north polarity due to the mid-portionof the armature being associatedwith the north pole of the permanent magnet 59. r The inductor planes52, 53, and 54 are made of soft iron and therefore are normally inert,but since thearmatures are polarized by the permanent magnets 58 and 59these armatures willremain magnetically biased to either associatedinductor plane pole piece to which they have been moved. Associated withthe pole piece 80 is a winding 60 which is adapted to be energized whena key 61, in the cap of the vehicle, is actuated and when energized iseffective to overcome the opposing bias produced by magnets 58 and 59andmoves the armature 56 into engagemen with the pole piece 80.

Referring now to Figs. 2, 3, and 4:, the trackw'ay magnets and theirinfluence on the receiver relay of Fig. '1 will next be described. Apermanent magnet trackway unit simply consists of a number of permanentbar magnets arranged to function as one large permanent magnet, with thepolarity as indicated on the drawing. This magnet is very powerfulcompared to thosev in the receiver and consequently, if thereceiver R ofFig. 1 1s passed over the permanent magnet unit the biasing efiectproduced repelling action will by magnets 58 and 59 will be overcome andarmatures 55, 56, and 57 will be rotated in a clockwise direction intothe position in which t iey are shown 1n Flg. 2, for the reason thatwhen the receiver unit passes within induc;

ture is of south polarity. The pole piece 80 assists the pole piece 79by the repelling action it has onthe armature 56. g

The electromagnet trackway elements shown in Figs. 3 and 4 are alike andconsist of rectangular units having the same general outline as thepermanent magnet 95. These units have four windings 96-99, inclusive.When the windings 98 and 99 are energized, a magnetic field of the samestrength as that of the permanent magnet is set up in the oppositedirection to that set up by the permanent magnet 95, as indicated inFig. 3. It will be obvious, therefore, that when the receiver passesover this trackway element, with the windings 98 and 99 energized,arm-atures-53, 56, and 57 will be rotated in a counter-clockwisedirection into the position in which they are shown in Fig. 1 and asdiagrammatically shown in Fig. 3.

If, alternatively, energized when the receiver R passes over theelectromagnet trackway element, as illustrated in Fig. 4, a magneticfield similar to, but at right angles to that set up by windings 98 and99 is set up and consequently, the pole piece of the inductor plane 54becomes of south polarity, while the pole pieces of the inductor planesnorth polarity. Since the polarityinduced in the inductor planes 52 and53 is the same, the efiect produced by them is substantially neutral andtherefore the associated armatures 55 and 56 remain in the position towhich they were moved by passing over a permanent magnet trackwayelement. 'The armature 57, however, is rotated in a counter-clockwisedirection due to the attractive influence set up in the pole piece 83 ofthe inductor plane 54; It should be noted that as the receiver relay Rpasses out of the inductive field of the electromagnet trackwayelements, the inductor planes 52 and 53 will pass through the field ofthe S poles of the trackway V magnetism of south polarity in the pole95, the pole piece of the :trated it is windings 96 and 97 are 52 and 53become of magnets which may induce weak.

the 'armatures 126 and127 in pieces of these inductor planes, butwithout effect since when they are of like polarity they will not tendto operate their armatures.

Referring now to'Figs. 5 and 5A, the track circuits-and arrangements ofthey trackway magnets will be described. In Fig.5 a portion of block A,a: block B, and a portion of a block O are shown; while in Fig. 5Aacontinuation of the block 0, a block D, and a portion of a block E areshown. blocks are divided. by track Th 1) is indicated. At the exit itwill be noted, a permanent magnet track way element is placed alongsidethe track. In advance of each of net trackway elementsis placed anelectromagnetic trackway. element.

insulation 100.

of each block,

SIX seconds will be consumed by a train traveling at'any speed above avery low speed 1n:travers1ng the dlstance between These these permanentmag e presence of vehicles in blocks A and block 7 Each of these magnetsis s'o'spa'ced that slightly more than V them. At the entrance of eachblock, a three position the trackway rails for controlling the currentsupply to the trackway element, located at the exit end of the adjacentblock and to 7 also supply current to a similar polarized trackway relayat the entrance end of the adjacent block. In. the trackcircuitsillusassumed thatthe block E and the next block in advance, thereof areboth unoccupied. -Under these circumstances, as will readily appearhereinafter, the current supplied to the rails of block E and thepolarized track relay105 will be in such a direction as to cause thearmatures 106 and 107 of this relay to be rotated into engagement withtheir left contacts. iVith the. armatures 106 and 107 in this positionan operating circuit for the polarized relay104, at

the entrance end of the block D, may be i traced from the negativeterminal of battery 121,1throughthe left contact and armature 106 of therelay 105, the armature 107 98 and 99 of the. electromagnetic trackwayelements, the rail 108, the winding ofthe polarized relay 104, to rail109, conductor 110, and to the positive terminal of the loattery 121.The current fiowto'the relay 104 is in the appropriate'direction tocause it to move itsarmatures126 and into engage ment with their leftcontacts, seam current suppliedover the block C to thepolarized rev,lay103 will be in the appropriate direction polarized relay isconnec'tedacross anditsleft contact, through the'windings i circuit forthepolarized relay 103 is com- 'pleted which extends from ductor 112, theresistance 111, the lower rail of block 0, through the. winding of relay103, the upper rail of block C, and the conposite direction to thatsupplied to ductor 150 to the negative terminal'of the battery 140. Thecurrent flow to the polariz'ed relay 103, it will be noted, is in theopthe relay 104 and therefore the polarized relay 103 rotates itsarmatures 136 and 137 into engagement with their right contacts; Withthe :armatures 136 and 137 in this position, current for operating thepolarized relay 102 at the" entrance of block D is supplied from thenegative terminal of battery 131, through the right'contact and armature136 of the polarized relay 103, armature 137 and its right contact,through the windings 97 and 96 of the. associated traclrwayelectromagnet, the lower rail of block B, the winding of the polarizedrelay 102, the upper rail of block B, and the conductor 160 tothe-positive-terminal of battery1131. The current flow to the polarizedrelay 102 is therefore in the same direction as that supplied to relays104 and 105 and consequently the armatures146 and 147 of the relay 102will bev rotated into engagement with their left contacts, therebycompleting circuits for feeding battery currentito the track relayof'the block A in thesa'me direction as it is being fed to the trackrelay 102. c

, \Ve will now consider thecircuits and apparatus under control of thearmatures 55, 56, and 57 of the receiver. These armatures as shown inFig. 1 are in the positions they assume while the vehicle is passingthrough a block which was entered under clear trafic conditions. Underthese circumstances, a circuit for; the green lamp 62 extends from thenegative terminal-or" the battery 34, over conductor '71, the armature57 and its cont-act member 57', contact 75, through the conductor 83,the armature 55 and its contact member. 55, the contact 73', conductor65, the lamp 62, conductor 69, conductor 67, contact 74, contact member56 and the associated armature 56, conductor 86 the contact andacknowledging key 61 to the positive terminal of the battery 64. Thegreen lamp 62 is therefore owing and serves to indicate to the enginemanthat the train is traveling under clear trafiic condi-" tions. Abranchrof the traced circuit extends over the conductor to and throughthe winding of anelectropneumatic valve EPV which is built into andforms a part of the brake valve structure. This valve when energize-(haspreviously explained, prevents the escape of air from the chambers 7 andare shown in Fig. 2.

and through 7 As the receiver R- passes oizerand within the influence o1thepermanent'magnet "trackway element 95 its armatures 55, 56, and57.are rotated into the position in which they Armature 55, at its contactmember 55, breaks a point in the traced circuit through contact 73' forthe green lamp 62, thereby" extinguishing the green, lamp and at itscontact 72 prepares a point in a circuit for the yellow lamp 63; at itsarmature 56 the traced circuit through contact'member56 and contact 73-through which ground was formerly supplied to the green lamp and to theelectronneumatic valve EPV is broken and consequently, theelectropneumatic valve EPV drops stem, thereby permitting air to exhaustfrom the chamher 7 2 through the port-74 9 and the whistle 5, whichaudiblywarns the engineman to be on the alert for a possible change ofsignal .indication; at armature 57' and'its associated contact member 57and contact- 7 5, a third point in the traced circuit for the green lamp62 is interrupted,and at the associated contact 7 6 a point in a circuitfor the red lamp 64 is prepared. r. 7 Since the associated elcctromagnettrackway element of-block A has its windings 98 and 99 energized thepolarit of this electromagnct is opposite to that or the permanentmagnet 95 and consequently, as the receiver passes over thiselectromagnet trackway element the armatures 55, 56, and are rotatedback into the position in which they are shown in Figs. 1 and 3. Thefor'merlytraced circuits for lighting'the green lamp- 62 and forenergizing the elcctropneumatic valve EPV-are therefore immediatelyreestablished and the a tuation of the whistle 5 ceases. These signalchangesscrveto indicate to the engineman that 1 they have entered ablock under favorable traiiic conditions, and therefore no action on thepart of the engineman is required. When the vehicle 101 reaches theexit'portion ofblocl: B, the receiver R passes over the permanent magnettrackway element 95, which causesthe armatures of the relay R :to beoperated to bring about. the same circuit changes as when the receiverpassed over the traclzway magnet 95. Since, how'- ever, the bloclrD isoccupied the trackway circuits the entrance to block C are such that thecaution windings96 and 9'? of the electromagnet trackway element,positioned a short distance in advanceof the permanent magnet tracltwayelement 95, are energized.

. Consequently, the magnetic iield set up by this "trachwayelectromagnet is at right angles to that set up by the l'jermanci 1tmagnet trackway element 95. When the receiverR Fig. 4:. Since thecircuitahead. Ordinarily, the engineman will heed the warning given by thewhistle 5 and will passes over this trackway electromagnet only thearmature 57- is restored, as illustrated in for the green lamp 62remains interrupted at contact 73 and contact member 55 and also atcontact member 56' and contact 74, the green lamp remains extinguished..Also, since the circuit for the electropneumatic valve EPV must alsopass through. contact member 56 and contact 74c, the electropneumaticvalve 're-' mains deenergized and the whistle 5 .0011- tinues to soundand serves to audlbly warn' the engineman of adverse trailic conditionsproceed to forestall an automatic brake application by operating theacknowledging key 61 momentarily. 'VVhen this key is operated, acircuitis completed for the armature restoring winding 60, viaconductors-85 and 71, and the armature56 is thereby restored to itsinitial position in which it is Shown in Fig. 1. cuit for theelectropneumatic valve EPV is thereforereestablished through contact 74,

and contact. member 56 as soon as the acknowledging key 61 isreturned.to its normal position. This results in the port 49 beingagain closedandin the whistle ceasing. operation. The. armature 57 in operating, at itscontact member 57 and contact 75 closed a point in the circuit of theyellow lamp 63 which is completed following the acknowledging actionfrom the negative terminal of the battery 84, through conductor 71',armature 57 and its contact member 57, the contact 75, conductor 88,armature 55, its contact member 55, contact 72, conductor66, the yellowlamp 63, conductor 69, conductor 67, contact 74,'contact member 56,conductor 86 and through the normal contacts of the acknowledgmg key 61to the positive terminal of the battery 84. The yellow lamp 63 istherefore lighted as the vehicle 101 progresses through block C anduntil the next signal change occurs as the vehicle passes over thepermanent trackway magnet When the receiver R passes over the track Waymagnets 95 the armatures 56 and 57 are again rotated into the positionin which they are shown in Fig. 2and consequently, the effectof havingpassed over the electromagnet trackway element at the exit of-block C isentirely wiped out. Since the block D occupied by a-vehicle 181, causingthe armatures 126 and 127 of the polarized relay 104 to assume theirneutral or mid position. the circuits through all windin s of theelectromagnet trackway element immediately in advance of the permanentmagnet trackway element 95 are open. The circuit conditions which areset up by the receiver R in passing over the trackway magnet 95therefore remains and since the whistle 5 continues to whistle 5silenced.

The formerly traced cir- 'trackway magnet 95 sound, the enginemen areaudibly informed that acknowledgment is again necessary.

Responsive to the acknowledging action, as in. the'case whenacknowledgment was made at the exit of block C, armature 56 while thearmatures 55 and 57 remain into attracted relations with respect to thepole pieces 78 and 82, respectively. The formerly traced circuit for theelect-ropneumatic valve EPV. is therefore again established and .the-

i A circuit is also complet- This circuit extends from the negativepoleof the battery 84, through conductor 71, the contactmember 57, contact76,-conductor 68, redlamp 6 1, the conductor 67,. contact 7.4, contactmember 5 and over the conductor 86 and thefacknowledging key 61 to thepositive terminal of the battery 84. The lighting of the red lampservesto warn the enginemen that are enteringa blockwhichis alreadyoccu-, pied and that they must'proce'ed with extreme caution. i i

It will now be assumed ed for the red lamp 7 that the engineman fails toacknowledge within the sixseconds of time interval allowed after passingthe Under these circum-' stances, atthe end of the six-second interval,sufficient air has been exhausted from the chamber72 out through thewhistle 5 to per mit the air pressure on the right side of the piston 19tobecome effective/to the valve member'20 to theleft. The movement ofthe valve member closes thenormally open passage extendingbetweenopenings 7 and 8 via port heading cock, th

moveit and,

7 port 10, and the double ereby preventing the brake pipe from beingrecharged while the slide valve member 20 is in its operated position.-The movement of the slide valve member also connects the port 10 to theservice exhaust port ll'viaby-pass 90, thereby causing a brake pipecause a service'brake application. 7 t g To release the brakes, after anautomatic application, the 'en'ginemanfmust first operate theacknowledging key 61 which, in a manner already described, is effectiveto energize the electropneumatie valve EPVand to complete. the circuitpressure reduction sufi icient to for the yellow or red lamp, dependingon'the condition ofthe re-- ceiver R. The energization' of the"electro-.

pneumatic valve EPV, as previously ex plained, stops the actuation ofthe whistle v5 and the exhaust of air from chamber 72. The air pressurein chambers 71Iand 7 2 therefore again rises at a-rate 22 and thecapacity soon as the pressure approximates that on the piston 19, thespring 21 will return thepiston 19 and the valve member 20 to theirnormal positions, in which they are shown, thus of the reservoir 50. Asrises toa point where it closing the passage 14. and again opening thedetermined by the'port 1 right side of the 7' 70 is rotated in, acounter-clockwise direction, i

. from the from the brake pipe via the port 10 If, after receiving anautomatic brake application, theengineman desires to amplify.

the application he can do so by'moving the handle of the brakeapplicator valve to the emergency position. This causes an instantaneousexhaust of air to occur through the emergency port of the brakeapplicator valve and results in av very quick reduction in pressurebeing made in the air pressure on the left side of the emergencyapplication piston 32. This permits the air on the right side of thepiston 32 to rapidly expand and move the emergency application piston 32to the left.

As soon as this piston has moved a slight d stance, its continuedmovement is assisted by air supplied to the right of the piston and theport 91. The movement of the piston 32 to the extreme left connects theport 10, via

by-pass 7 3 to the. large emergency exhaust port 37. This quickreductionin the brake line results in an emergency application of thebrakes.

It has been proposed that installations of cab signalling be madewithout the provision of any train stop equipment. The present system isideal for an installation j of this kind, In an installation of thiskind, theelectropneumatic valve EPV and whistle 5 or their equivalentwill be connected directly with, the main reservoir; the visual andaudible signalcontrol equipmentwill function in the same manner as whenused in conjunction with the brake applicator valve; and: the enginemanwill be required to acknowledge as inthe trainstop system.

From the foregoing it will be appreciated thatapplicant has succeededin" developing train control and the cab signalling equipment which isvery simple and will operate in an absolutely reliable manner. 7

What is claimed is:

1. In a train stop system, vehicleequipment including cab signal lampsfor indicat- -ing clear, caution, and danger traffic initiated will ventvalve through conditions, an automaticbrakecontrol device for initiatinga brake application, an audible warning signal operable each time anautomatic brake application is initiated, and a receiver relay andacknowledging key operable tomaintain full control over said signals andbrake controldevice. q

2. In the vehicle carried equipment of a train stop system, a set oflamp si nalsfor indicating fclear, caution,

trafiicconditions, a [receiver relay having three two position armaturesmovable to record three different trafiic conditions,a set ofacknowledging contacts, and clrcuitsfor said signals-including thearmatures and contacts of said relay andof said acknowledging contactsexclusively. Y

3. An automatic train control system comprising automatic brake controlvalve super imposed upon an air brake system of the normally chargedbrake pipe type, which if the brake pipe to atmospheric pressure, meanscontrolled in accordance with, traffic conditions in advance forinitiating the actuation of said brake control valve under unfavorabletraffic conditions ahead, acknowledging means including con tactsmanually operable by. the engineeer to stop the venting of the brakepipe, a timing reservoir normally connected to atmosphere, and means forclosing said reservoir to atmosphere consequent to the operation of theand danger acknowledging means to delay the stopping of the ventinguntil a definite time period, following theoperation of the acknowledgmgmeans, has elapsed. 1

4. In an automatic train control system superimposed upon a brakingsystem of the normally charged brake pipe type, a slide which the brakepipe is normally charged from the usually provided engineers brakevalve, ports in said slide valve forcausing the venting of the brakepipe to atmosphere, when the slide valve actuates,'to

produce an automatic brake application, a timing reservoir normallyconnected to at-' mosphere; means in said valve, when in thebrakeapplying position, for employing said reservoir to limit the timeduring which the venting continues," and a magnet valve operated upon anacknowledging act on the part of the engineer to close the connectionbetween thereservoir and atmosphere to make the same eflective for'thepurpose set In witness whereof, I hereunto subscr1be my name this26th'day of October, A. D. 1931. ALFRED ERNEST I-IUDD.

forth.

